Study on the inspection technique and maintenance solution for BOSS welds

The BOSS which is also called the set-on branch connection is a new structure used in nuclear power plant in recently years. The BOSS weld failure may lead to borated water leakage, and it will probably affect the safety of the equipment in the pressurized water reactor nuclear power plants (PWRs). In this study, causes of BOSS weld failures were studied first. Then through the technique features of radiographic inspection, an applicable inspection technique for BOSS welds in PWRs was summarized. Combining the experience feedback of BOSS weld failures at home and abroad, a useful maintenance solution was proposed. In the end, some feasible suggestions for improving the quality of BOSS welds were established from the point of views of design process, welding process and inspection process.